Rotary steam engines are well known in the art. Early constructions may be found in patents to Fisher U.S. Pat. No. 137,065; Shepard U.S. Pat. No. 525,121; Taylor U.S. Pat. No. 597,793; Taylor U.S. Pat. No. 949,605; Gross U.S. Pat. No. 968,653; and Conklin U.S. Pat. No. 1,270,498. See also Plummer U.S. Pat. No. 2,454,006; Farrell U.S. Pat. No. 3,109,382; Eyer U.S. Pat. No. 3,236,187; Nardi U.S. Pat. No. 3,865,5221; Gardiner U.S. Pat. No. 4,393,829 and Nardi U.S. Pat. No. 5,039,290.
In this type of steam engine there is no reciprocating piston. Instead each piston (virtual) is partially confined in an output nesting arrangement and moves continuously in one direction. The inner transverse edge of each piston engages and slides along the cylindrical surface of a stationary inner body (cylinder head). The inner body carries a plurality of rotatable elements/virtual pistons (ordinarily one more than the number of virtual cylinder heads) nested for rotation in a succession of cavities in the inner body.
The rotatable elements/virtual pistons act to form the ends of the curved cylinders. The construction permits the piston on reaching the end of its stroke, to pass the virtual cylinder head to move into the next cylinder.
The radially outermost part of each virtual piston forming the end of the cylinder is in steam tight fixed gap arrangement with the walls of the cylinder.
In order that the piston may pass the virtual cylinder head, it is essential that the piston and the virtual cylinder head be in a form which might be said to be roughly in the nature of paired gear teeth. Thus the piston would represent an internal tooth, designed to cooperate with external teeth on the virtual cylinder head.
In some of the early forms disclosed in the prior art, it was considered desirable to gear the rotating part of the engine to the non-rotatable element in such manner that when the piston reached the rotatable element, the latter would be positively rotated by the gearing so that the piston would enter a complementary cavity in the rotatable element and thus to pass thereby. In other forms in the prior art, the piston came into positive engagement with one of the stationary blades of the rotatable element and forced the blade to rotate, thereby permitting passage of the piston into the next curved cylinder.
In all of the prior constructions, the shape of the piston and the shape of the blades of the rotatable elements did not provide for efficient passage of the piston past the rotatable element. There was a leakage of steam, shock, excessive condensation, undue wear of the engaging portions, inefficiency in the location of the exhaust ports, inefficiency in the performance of the steam admission ports and inability to change the time of steam cut-off.
In my prior invention, U.S. Pat. No. 5,039,290 the outer housing was stationary. The piston was a free floating piston and had no shaft.
Broadly my invention is a positive displacement, single expansion pressure articulated expander, like a turbine i.e., it has no compression cycle. The engine is designed to operate on saturated steam at moderate temperatures and pressures (475xc2x0 F. and 500 psi). At these temperatures, a 5% mixture of lubricating oil can, if desired (but not necessarily) be admitted to the steam directly. In general terms, the engine can be classified as a positive displacement turbine.
A steam turbine""s longevity (20 years) is based on 100% fixed gap clearance; i.e., no metal to metal contact. The present invention has a fixed gap clearance of about 80%. The remaining components are pressure balanced which minimizes metal to metal contact.
The engine of the preferred embodiment has a high power/weight ratio (2 lbs./HP least admission, 0.5 lbs./HP full admission). It is equivalent to a 12 cylinder internal combustion engine because there are 6 power strokes per revolution. Furthermore, it has a wide power rangexe2x80x940.05-1 megawatt and the possibility of 40% thermal efficiency.
In the present invention, cylinder heads are fixed to the outer stationary wall of the engine. The inner edge of each cylinder head has a fixed gap through which slides the cylindrical surface of a rotatable power shaft assembly, which shaft assembly has a plurality of nests. Received in each of the nests is a virtual piston having lobes which allow free movement of the pistons in the nests. Adjacent lobes define troughs. The outer edges of the troughs are in sliding engagement with the inner surface of the nest and there is a small fixed gap 0.0015xe2x80x3 clearance with the inner surface of the fixed outer wall of the engine. Further, the outer surfaces of the lobes cooperate closely with the outer surfaces of the cylinder heads. Thus, the major portion of each piston has substantially the reverse configuration of the walls of the cylinder head. However, the design is such that an acceleration/deceleration ramp can be accomplished by initiator and admission cycles.
The virtual piston within the nest is balanced at all times (except when in contact with the cylinder head). Specifically, the cylinder head vertex effectively reduces the area on the face of contact about its axis of rotation within the nest but is imbalanced with reference to the center of rotation of the dual-nested power shaft assembly. Upstream of the cylinder head is an exhaust port. As the facing surface of a first lobe approaches the exhaust port, a chamber is defined by the inner surfaces of the stationary walls, the surface of the cylinder head opposing the facing surface of the lobe, the outer surface of the power transfer shaft and the surface of the lobe next preceding the first lobe. As the first lobe passes the exhaust port, the exhausting ceases and virtual piston (VP) acceleration is applied by an initiator. The shaft assembly continues to rotate in a counterclockwise direction, while clockwise rotation is imparted to the virtual piston by the initiator. As rotation continues, the first lobe engages the opposed surface of the cylinder head.
The shaft assembly continues to rotate in the counterclockwise direction. The virtual piston always rotates in the clockwise direction. A new volume is defined on the other side of the cylinder head between the surface of the next preceding lobe facing the opposed cylinder head surface, and the facing surface of the first lobe. Steam is introduced from the cylinder head into this volume tending to drive the free piston in a counterclockwise direction. The piston is unbalanced but cannot rotate in a counterclockwise direction because it is prevented from doing so at this time by contact with the vertex of the cylinder head and the large side roller. The force created by the introduction and expansion of the steam in the closed chamber continues to drive the shaft assembly in the same direction (ccw).
In the preferred embodiment, there are three cylinder heads spaced 120xc2x0 apart and two virtual pistons spaced 180xc2x0 apart. Thus, there is always at least one steam cylinder in operation and there never will be any position of dead center. As a result, the rotation of the inner shaft assembly is continuous and the driving force provided by this stream is substantially uniform.